1.

Prove the followings identities:(1 – sinθ)(1 + sinθ) = cos2θ

Answer»

Taking LHS = (1 – sinθ)(1+ sinθ)

Using identity , (a + b) (a – b) = (a2 – b2) , we get

= (1)2 – (sinθ)2

= 1 – sin2 θ

= cos2 θ [∵ cos2 θ + sin2 θ = 1]

= RHS

Hence Proved



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